Prefilled syringe with breakaway force feature

ABSTRACT

A jet injector that includes a prefilled syringe. The syringe includes a fluid chamber that contains a medicament. The syringe also has an injection-assisting needle, and a plunger is movable within the fluid chamber. A housing is configured for allowing insertion of the needle to a penetration depth. The housing includes a retractable guard and an interference component, e.g., a lock ring, adjacent to the retractable guard that interferes with the movement of the retractable guard. An energy source is configured for biasing the plunger to produce an injecting pressure to jet inject the medicament from the fluid chamber through the needle to an injection site.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of pending U.S. application Ser. No.13/785,582, filed Mar. 5, 2013, which claims the benefit of priorityfrom U.S. Provisional Application Ser. No. 61/607,339 filed Mar. 6,2012, all of which are hereby incorporated by reference in theirentireties. All patents, patent applications, and references citedanywhere in this specification are hereby incorporated by reference intheir entirety.

BACKGROUND OF THE INVENTION

The present invention relates to a jet injector and in some embodimentsa needle-assisted jet injector that uses a low jet injection pressureand has a lock ring that provides breakaway force resistance.

Certain jet injection devices have needle guards that must be retractedprior to insertion of the needle and triggering of the jet injection. Acertain amount of force is normally required to trigger the jetinjection. To assure sufficient needle guard travel for needle insertionand triggering, it is at times desirable to require a breakaway forceprior to significant needle guard retraction to assure that insertion ofthe needle and triggering of triggering force is overcome. The presentinvention addresses this problem.

SUMMARY OF THE INVENTION

In certain embodiments, the invention relates to a jet injector. In oneembodiment, the jet injector includes a prefilled syringe having acontainer portion defining a fluid chamber containing a medicament; aninjection-assisting needle disposed at the distal end of the chamber,having an injecting tip configured for piercing an insertion location,and defining a fluid pathway in fluid communication with the chamber forinjecting the fluid from the chamber into an injection site; a plungermovable within the fluid chamber; a housing that houses the prefilledsyringe and is configured for allowing insertion of the needle at theinjection location to an insertion point that is at a penetration depthbelow the surface, the housing including: a retractable guard that ismovable between a protecting position in which the needle is disposedwithin the guard and an injecting position in which the tip of theneedle is exposed for insertion to the insertion point, and aninterference component adjacent to the retractable guard that interfereswith the movement of the retractable guard when the retractablecomponent is moved at least partially from the protecting positiontoward the injecting position; a syringe support supportively mountingthe prefilled syringe in the housing; an energy source configured forbiasing the plunger with a force selected to produce an injectingpressure on the medicament in the fluid chamber to jet inject themedicament from the fluid chamber through the needle to the injectionsite.

In certain embodiments, the energy source and prefilled syringe areconfigured such that the injecting pressure remains between about 80p.s.i. and about 1000 p.s.i. during injection of the medicament. In oneembodiment, the energy source and prefilled syringe are configured suchthat the injecting pressure remains below about 500 p.s.i. and aboveabout 90 p.s.i. during the injection of the medicament. In anotherembodiment, the energy source and prefilled syringe are configured toproduce the injecting pressure that remains at least at about 100 p.s.i.during the injection of the medicament. In one embodiment, the energysource and prefilled syringe are configured such that the injectingpressure remains up to about 350 p.s.i. during the injection of themedicament.

In certain embodiments, the prefilled syringe has a distal portion inwhich the injection-assisting needle is located, and a proximal portionopposite the distal portion; and the syringe support axially supportsthe proximal portion of the pre-filled syringe during the jet injectionof the medicament, such that the distal portion of the prefilled syringeis substantially unsupported in an axial direction. In one embodiment,the container portion of the pre-filled syringe is made of blown glass.In another embodiment, the injection-assisting needle is adhered to theglass.

In certain embodiment, the interference component is a ring having atleast one abutment arm extending distally from a proximal enddimensioned to fit within the housing, the abutment arm having at leastone tapered portion. In one embodiment, the at least one abutment armhas an engagement portion axially adjacent to the at least one taperedportion that is configured to cause resistance to the movement of theretractable guard when the retractable guard is moved at least partiallyfrom the protecting position toward the injecting position. The abutmentarm may include a first abutment arm face. The injection device mayinclude a second abutment arm having a second abutment arm face.

In one embodiment, the energy source comprises a spring. In oneembodiment, the jet injector further includes a ram that is biased bythe spring against the plunger to produce the injecting pressure,wherein the ram comprises a bell portion on which the spring is seated,and the bell portion defines a hollow interior configured for receivingthe prefilled syringe when the device is fired, such that the springsurrounds the prefilled syringe.

In some embodiments, the jet injector further includes a triggermechanism operably associated with the energy source for activating theenergy source to jet inject the medicament, wherein the triggermechanism is configured for activating the energy source after theretractable guard is retracted from the protecting position. In oneembodiment, the retractable guard is operably associated with thetrigger mechanism to cause the trigger mechanism to activate the energysource when the guard is retracted to the injecting position.

In some embodiments, the interference component is a sleeve having anengagement portion extending outwardly from an outer surface of thesleeve that is configured to cause resistance to the movement of theretractable guard when the retractable guard is moved at least partiallyfrom the protecting position toward the injecting position. In otherembodiments, the interference component is a latch coupled to thehousing that is configured to cause resistance to the movement of theretractable guard when the retractable guard is moved at least partiallyfrom the protecting position toward the injecting position.

In certain embodiments, the housing is configured for allowing insertionof the needle to the penetration depth, which is between about 0.5 mmand about 5 mm below the surface at the insertion location.

In certain embodiments, the housing is configured for allowing insertionof the needle to the penetration depth, which is between about 11 mm andabout 13 mm below the surface at the insertion location.

In certain embodiments, the chamber contains about between 0.02 mL andabout 4 mL of the medicament.

In certain embodiments, the penetration depth and injecting pressure aresufficient to substantially prevent backflow of the injected medicament.

In other embodiments, the jet injector further includes a syringecushion associated with the syringe support and prefilled syringe tocompensate for shape irregularities of the pre-filled syringe.

In certain embodiments, the invention relates to a lock ring for a jetinjector. In other embodiments, the lock ring includes at least oneabutment arm extending distally from a proximal end of a bodydimensioned to fit within in a housing of the jet injector, the abutmentarm having at least one tapered portion and at least one engagementportion axially adjacent to the at least one tapered portion, theengagement portion being configured to cause resistance to the movementof a retractable guard of the jet injector; and at least one flapradially adjacent to the at least one abutment arm extending distallyfrom the proximal end of the body.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofembodiments of the present invention, will be better understood whenread in conjunction with the appended drawings of exemplary embodiments.It should be understood, however, that the invention is not limited tothe precise arrangements and instrumentalities shown.

In the Drawings:

FIG. 1 is a side view of an embodiment of a jet injector constructedaccording to the present invention, showing the injector prior toinjection;

FIG. 2 is a cross-sectional view of the jet injector of FIG. 1 thereoftaken along plane II-II;

FIG. 3 is a perspective view of a prefilled syringe for use in the jetinjector of FIG. 1;

FIG. 4 is a perspective view of a syringe cushion of the jet injector ofFIG. 1;

FIG. 5 is a cross-sectional view of the jet injector of FIG. 1, showingthe injector at the start of the jet injection;

FIG. 6 is a graph showing the pressure present in the polluted chamberover time that contains medicament in an embodiment during jetinjection;

FIG. 7 is a side view of another embodiment of an injector that isconfigured for using a narrow diameter prefilled syringe;

FIG. 8 is a cross-sectional view of the jet injector of FIG. 1; takenalong plane VIII-VIII; VIII;

FIG. 9 is a cross-sectional view of another embodiment of an injectorusing a needle for intramuscular jet-injection;

FIG. 10A is a side view of an interference component of a jet injectorin accordance with an exemplary embodiment;

FIG. 10B is a perspective view of an interference component of a jetinjector in accordance with an exemplary embodiment; and

FIG. 11 is a graph showing the breakaway force over time of an jetinjector in accordance with an exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the accompanying drawings, various embodiments of thepresent invention are described more fully below. Some but not allembodiments of the present invention are shown. Indeed, variousembodiments of the invention may be embodied in many different forms andshould not be construed as limited to the embodiments expresslydescribed. Like numbers refer to like elements throughout. The singularforms “a,” “an,” and “the” include the singular and plural unless thecontext clearly dictates otherwise.

Referring to FIGS. 1 and 2, an embodiment of an injector 10 has ahousing 12 configured for allowing a user to handle the injector 10. Thehousing 12 includes an outer housing member 14 that substantially housesmost of the components shown in FIG. 2. A syringe support member 16 ishoused within and mounted with the housing 12. The syringe supportmember 16 is configured to hold and position a prefilled syringe 18,which is shown in FIG. 3. In one embodiment, the syringe support member16 is substantially fixed to the housing 12, such as by snaps, anadhesive, a weld, or another known attachment. The prefilled syringe 18has a container portion 20 that defines in its interior a fluid chamber22, which is prefilled with medicament to be injected. At the distal endof the prefilled syringe 18 is an injection-assisting needle 24. Needle24 has an injecting tip 26 configured as known in the art to penetratethe tissue of a patient, in certain embodiments, the skin of thepatient. A needle bore extends through the needle 24, as known in theart. The bore is in fluid communication with the medicament in the fluidchamber 22 and is open at the needle tip 26 to inject the medicament.

At a proximal side of the fluid chamber 22, opposite from the needle 24,is a plunger 28 that seals the medicament in the fluid chamber 22. Incertain embodiments, a syringe wall 30 comprises a tubular portion, insome embodiments closed at a distal end and open at a proximal end, todefine the fluid chamber 22. Plunger 28 is slideably received in thetubular portion. The prefilled syringe 20 is configured such that whenthe plunger 28 is displaced in a distal direction, the volume of thefluid chamber 22 is decreased, forcing the medicament out therefrom andthrough the bore of the needle 24.

At the distal end of the fluid chamber 22 is a needle hub portion 32 towhich the needle is mounted. In one embodiment, a syringe flange 34extends radially from the proximal end of the syringe wall 30.

In one embodiment, the syringe 18 has a syringe body 36 that includesthe flange 34, wall 30 and hub portion 32. In one embodiment, syringebody 36 that includes flange 34, wall 30, and hub portion 32 is ofunitary construction. A preferred material for the syringe body 36 isglass, but other materials can be used in other embodiments. A suitableprefilled syringe is the BD Hypak™, which is available in various sizesand volumes and is sold prefilled with medicament. The glass of thesyringe body 36 is adhered to the needle 24. Typical medicaments andmedicament categories include epinephrine, atropine, sumatriptan,antibiotics, antidepressants, and anticoagulants. Using a prefilledsyringe 18 facilitates handling of the medicament when the injector 10is assembled, and there is an extensive body of knowledge of how themedicaments keep and behave in a prefilled syringe.

A syringe cushion 38, which is shown in detail in FIG. 4, is in certainembodiments made of an elastomeric material or other resilient material.A flange 40 of the syringe cushion 38 extends radially and is disposedand serves as an interface between the distal side of the syringesupport member 16 and the syringe flange 34. Elevated portions, such asnubs 42 extend proximately from the cushion flange 40 and are configuredand dimensioned to abut the syringe flange 34.

Prefilled syringes that are manufactured by a blown glass process canhave significant dimensional tolerances and unevenness, particularly inthe glass body 36. The cushion 38 can serve to accommodate the shapeirregularities and to properly position and locate the prefilled syringe18 within the syringe support 16. Typically, the axial thickness ofglass blown syringe flanges on a 1 mL prefilled syringe is within about±0.5 mm. For a BD Hypak™ 1 mL standard prefilled syringe, the thicknessof the syringe flange 34 is 2 mm+0.5 mm or −0.4 mm, and in a 1 mL longconfiguration BD Hypak™ syringe, the flange axial thickness is about1.65 mm±0.25 mm. Other dimensional variations that occur in typicalglass prefilled syringes are in the internal and external diameters ofthe tubular wall 30. These variations can be accommodated by theresilient sleeve portion 44 of the syringe cushion 38, which extendsaxially around the interior of the syringe support 16. In oneembodiment, the syringe cushion 38 is received in the interior of thesyringe support member 16 and receives the syringe body 36, in certainembodiments fitting snugly therein.

In one embodiment, the sleeve portion 44 has radially inwardly extendingprotrusions 46 with a surface area and configuration selected to allowthe insertion of the prefilled syringe 18 therein during assembly, butproviding sufficient friction to maintain the syringe 18 in place and toprovide cushioning and shock absorption during the firing of theinjector 10. Outward protrusions 48 are also provided on the sleeveportion 44, which can be received in corresponding recesses of thesyringe support 16 to prevent axial rotation therebetween. Recessedareas 50 can be provided on the interior and exterior of the syringecushion 38 opposite corresponding protrusions 48 on the opposite radialside of the sleeve portion 44 if an increased wall thickness of thesleeve portion 44 is not desired. In an alternative embodiment one orboth of the flange 40 and sleeve 44 of the syringe cushion 38 aresubstantially smooth, substantially without any protrusions. In oneembodiment, the material and configuration of the syringe cushion 38 isalso sufficient to entirely support the prefilled syringe 20 towithstand a firing force applied axially in a distal direction on theplunger 28. Thus, the entire support for the prefilled 20 can beprovided on the syringe flange 34, while the distal end of the syringe18 may itself be substantially unsupported in an axial direction. Thiscan help withstand the shock on the glass body 36 of the prefilledsyringe 20 produced by the elevated pressures within the fluid chamber22.

To radially position the distal end of the prefilled syringe 18, thesyringe support 16 in certain embodiments has a narrowed bore portion 51that is in certain embodiments configured to abut the outside of thesyringe wall 30. This is especially beneficial when the needle 24 isinserted into the patient's skin. The narrowed bore portion 51 can bemade of a resilient material, such as an elastomer, or it can be madeunitarily with the rest of the syringe support 16, in certainembodiments of a plastic material.

Referring to FIG. 2, in one embodiment, a trigger mechanism 52 is alsohoused within housing 12. The trigger mechanism 52 includes an innerhousing 54 that can be attached to the outer housing 14, such as bysnaps, an adhesive, a weld, or other known attachment. Triggerprotrusions 56 extend inwardly from the proximal end of the innerhousing 54 and are resiliently biased outwardly. Trigger protrusions 56are received in a recess 58 of ram 60 in blocking association therewithto prevent distal movement of the ram 60 prior to the firing of thedevice. The ram 60 is urged towards the distal end of the injector 10 byan energy source, which in certain embodiments is a compression spring52, although other suitable energy sources can alternative be used suchas elastomer or compressed-gas springs. In one embodiment, thecompression spring is a coil spring.

A trigger member of the trigger mechanism 52, such as a latch housing64, is provided exterior to the inner housing to retain the triggerprotrusions 56 in the blocking association in the recess 58 to preventpremature firing of the injector 10. The latch housing 64 is slideableinside the outer housing 14 with respect to the inner housing 54, incertain embodiments in an axial direction, and the latch housing 64 incertain embodiments surrounds the inner housing 54.

The housing 12 has a needle guard 66 that is moveable with respect tothe outer housing 14. The needle guard 66 is shown in FIGS. 1 and 2 in aprotecting position, in which the needle 24 is disposed within the guard66. The needle guard 66 is retractable, in one embodiment into the outerhousing 14, in a proximal direction to an injecting position, in whichthe needle tip 26 and an end portion of the needle 24 is exposed asshown in FIG. 5 for insertion into a patient. In one embodiment, theproximal movement of the guard is prevented substantially at theinjecting position.

In one embodiment, an interference component 134 interferes with themovement of the needle guard when the needle guard is moved at leastpartially from the protecting position toward the injecting position.

In one embodiment, the housing 12 has an interference component 134,e.g., a lock ring, adjacent to the needle guard 66, the interferencecomponent 134 interferes with the movement of the needle guard when theneedle guard is moved at least partially from the protecting positiontoward the injecting position. Interference component prevents movementof the needle guard until the breakaway force 146 is exceeded. Theinterference component 134 is shown in FIGS. 10A and 10B. In oneembodiment, the interference component 134 is included as part of a ringhaving at least one abutment arm 136 extending distally from a proximalend 138 dimensioned to fit within the housing 14, the abutment arm 136having at least one tapered portion 140. The abutment arm 136 may alsohave an engagement portion 142 axially adjacent to the at least onetapered portion 140 that is configured to cause resistance to themovement of the needle guard 66 when the needle guard 66 is moved atleast partially from the protecting position toward the injectingposition. While interference component 134 may have more than oneabutment arm 136 and correspondingly more than one engagement portion142, certain embodiments include only one abutment arm 136 having anengagement portion 142. The interference component may also include atleast one flap 144 radially adjacent to the at least one abutment arm136 extending distally from the proximal end 138 of the interferencecomponent 134.

The interference component 134 may also be coupled to the housing 12,incorporated in a sleeve separate from the housing 12, or include alatch.

Referring to FIG. 11, breakaway force 146 is needed to overcome theresistance on the needle guard 66 caused by the engagement portion 142when the needle guard 66 is moved at least partially from the protectingposition toward the injecting position. Referring to FIG. 11, breakawayforce 146 is the resistance to retraction that is exerted on the needleguard 66 when an initial attempt to retract the needle guard 66 occurs.Breakaway force 146 is a distinct force from the triggering force 148that is needed to cause jet injection of the medicament and is a greaterforce than that provided by the spring 62 that biases the needle guard66 in the extended position. Breakaway force 146 is sometimes also agreater force than what occurs due to the friction of the needle guard66 retracting motion sliding on other mating components in the device.In one embodiment the breakaway force 146 is controlled and only occursas a single event.

Referring to FIG. 2, the needle guard 66 is associated with the latchhousing 64 such that when the guard 66 is displaced distally it slidesthe latch housing 64 also in a distal direction to release the triggerprotrusions 56 from the recess 58. In one embodiment, the latch housing64 has a latching portion 68 that abuts the inner housing 54 in anassociation to bias and maintain the trigger protrusions 58 positionedin the blocking association with the ram 60 prior to the firing of thedevice 10. When the latch is slid proximately by the retracting of theguard 66 to the injecting position, the latching portion 68 slidesbeyond the portion of inner housing 54 that is contacts to flex thetrigger protrusions 56 into the recess 58 of the ram 60, allowing thetrigger protrusions 56 to move radially outwardly from the recess 58 andtherefore from the blocking association. When this happens, spring 62biases the ram 60 against plunger 28 to fire the jet injector 10. Incertain embodiments, latch housing 64 defines trigger openings 70adjacent to latching portions 68, which is configured to receive aportion of the inner housing 54, such as the surface disposed radiallyoutwardly from the trigger protrusions 56.

In certain embodiments, the guard 66 is resiliently biased distallytowards the protecting position by compression coil spring 72. Also, theneedle guard 66 has an axial opening 74 to allow the needle 24 passthere through, and which may be sized according to the type of injectordesired. The construction of the present embodiment allows a user topush the distal end of the injector 10 against the patient's skin,pushing the needle 24 into the skin at an insertion location,substantially at the same speed as the injector is pushed. Once theneedle 24 is fully inserted to an insertion point at a penetrationdepth, the trigger mechanism 56 fires the jet injection to an injectionsite.

Referring to FIG. 5, in one embodiment, the prefilled syringe 18 and itsneedle 24 are not shuttled forward automatically into the patient'sskin, such as by the firing energy source during the injection firing.The user preferably gently pushes the entire device forward to insertthe needle 24, in certain embodiments retracting a guard against theskin in the process. In one embodiment, the prefilled syringe 18 issubstantially stationary within the housing 12, and, in one embodiment,is substantially fixed thereto. In this manner, the present inventionprovides for a gentler treatment of the syringe during injection thatenables the use of a sufficiently powerful spring 62 or other energysource to produce a jet injection without the risk of damaging therelatively fragile and complex shapes of the prefilled syringe, alsoallowing, for example, the injection of high viscosity solutions, wherethe risk of breaking a syringe, such as at the flange, is elevated inprior art injectors that shuttle the syringe forward in the housing andinto the patient. Residual stresses are also often present in the glassbodies of prefilled syringes, and this configuration reduces theadditional stresses imposed thereon during use, further protecting thesyringe. Also, misalignments in the prefilled syringe are also renderedoperationally less significant due to the gentle insertion of the needlethat is possible with this configuration.

In one embodiment, the injecting position of the guard 66 is such that apredetermined length of the end of needle 24 is exposed from the guard66. In some embodiments, such as where the opening 74 is of asufficiently large diameter, the skin of the patient maybe allowed toextend into the opening 74 when the device 10 is pressed there against,and a needle that does not protrude beyond the distal end of the guard66 can be used while still penetrating the skin to a certain depth. Inmost embodiments, the distance 76 by which the needle tip 26 extendspast the distal end of the guard 66 will be fairly close to the depth ofthe insertion of the needle.

In one embodiment, such as for subcutaneous injection, the guard 66 isconfigured to allow insertion of the needle 24 to a penetration depth inthe skin that is up to about 5 mm below the skin surface. In anotherembodiment, the penetration depth is less than about 4 mm, and in oneembodiment is less than about 3 mm. In one embodiment, the insertiondepth is at least about 0.5 mm and, in other embodiments, at least about1 mm. In another embodiment, the distance 76 by which the needle extendspast the guard 66 or the distal surface of the guard 66 that contactsthe skin is up to about 5 mm, in one embodiment, up to about 4 mm, andin another embodiment up to about 3 mm. In certain embodiments,extension distance 76 is at least about 0.5 mm, in one embodiment atleast about 1 mm, and in another embodiment at least about 2 mm. In oneembodiment, tip 26 extends by a distance 76 of around 2.5 mm beyond theportion of the guard 66 that contacts the skin in the injectingposition.

In another embodiment, such as for intramuscular injection, the injectoris configured to allow the needle 24 to be inserted into the patient toa penetration depth in the skin, or alternatively beyond the distalsurface of the guard, by a distance of up to about 15 mm. In oneembodiment, this distance is about between 10 mm and 14 mm. In anembodiment for jet injection of epinephrine for instance, a penetrationdepth or distance beyond the guard is between about 11 mm and about 17.0mm, and, in other embodiments, between about 13 to about 15 mm. Jetinjection with this length needle improves the distribution of themedicament in the patient tissue compared to non jet injection. Otherexposed needle lengths can be selected for jet injection to differentdepths below the skin, with, in certain embodiments, an overallpenetration length of between about 0.5 mm and about 20 mm. In certainembodiments, the needle guard is configured for retracting from aprotecting position, in one embodiment covering the entire needle 24(See FIG. 2), to an injecting position, in which the desired length ofthe end of the needle 24 is exposed (See FIG. 5).

In some embodiments, the spring 62 and the prefilled syringe 18 areconfigured to jet inject the medicament. Thus, the spring 62 applies aforce on the plunger 28 that is sufficient to elevate the pressurewithin the fluid chamber 22 to a level high enough to eject themedicament from the needle 24 as a jet. Jet injection is to beunderstood as an injection with sufficient velocity and force to drivethe medicament to locations remote from the needle tip 26. In manual andautoinjector-type injections, in which the injection pressures are verylow, the medicament exits the needle tip inside the patient and istypically deposited locally around the needle in a bolus. On the otherhand, with the present jet injection device 10, the medicament is jetinjected distally or in other directions, such as generally radially bythe elevated pressure jet, which beneficially improves the distributionof the medicament after the injection and keeps a large bolus fromforming that can detrimentally force the medicament to leak back out ofthe patient around the needle or through the hole left behind by theneedle after it is removed.

Referring to the graph shown in FIG. 6, numeral 78 represents the pointin time when device 10 is fired, and numeral 80 represents the point intime of completion of the medicament injection, in certain embodimentswhen the plunger 28 hits the forward wall of the container portion 20.Numeral 82 represents the initial and peak pressure during theinjection, and numeral 84 represents the final and low pressure duringthe injection. Since the spring 62 of one embodiment has a linear springconstant and an injection-assisting needle is used to puncture the skinbefore commencing the injection, the pressure drops substantiallylinearly from the start of the injection 78 until the injection iscompleted. The final pressure 84 at the end 80 of the injection issufficiently elevated so that even at the end of the firing stroke ofram 60, the medicament is still jet injected, and a very small amount ornone of the medicament is deposited in a bolus around the needle tip 26.

In one embodiment, the peak pressure during the injection is less thanabout 1,000 p.s.i., in one embodiment less than about 500 p.s.i., and inanother embodiment less than about 350 p.s.i. At the end 80 of theinjection, the pressure 84 applied to the medicament in the fluidchamber 22 is in one embodiment at least about 80 p.s.i., in oneembodiment at least about 90 p.s.i., and in another embodiment at leastabout 100 p.s.i. In one embodiment of the invention, the initialpressure 82 is around 330 p.s.i., and the final pressure is about 180p.s.i., while in another embodiment the initial pressure 82 is about 300p.s.i., dropping to around 110 p.s.i. at the end 80 of the injection.The needles used in these embodiments are between 26 and 28 gauge, andare in certain embodiments around 27 gauge, but alternatively otherneedle gages can be used where the other components are cooperativelyconfigured to produce the desired injection. In an embodiment for jetinjection of epinephrine for instance, certain embodiments of theneedles are between 20 and 25 gauge, and in other embodiments, 22 gauge.In one embodiment, the components of the injector 10 are configured tojet inject the medicament to a subterraneous injection site.

The amount of medicament contained and injected from fluid chamber 22 isin one embodiment between about 0.02 mL and about 4 mL, in certainembodiments less than about 3 mL, and in other embodiments is around 1mL. Larger volumes may also be selected depending on the particularmedicament and dosage required. In one embodiment, the prefilled syringeis assembled into the remaining parts of the jet injector 10 alreadycontaining the desired amount of medicament. In one embodiment, theprefilled syringe contains about 1 mL of medicament.

In one embodiment, injection rates are below about 0.75 mL/sec., in oneembodiment preferably below about 0.6 mL/sec., in one embodiment atleast about 0.2 mL/sec., in one embodiment at least about 0.3 mL/sec,and in other embodiments at least about 0.4 mL/sec. In one embodiment,the injection of the entire amount of medicament is completed in lessthan about 4 seconds, in one embodiment in less than about 3 seconds,and in other embodiments in less than about 2.5 seconds. In oneembodiment, the medicament injection takes at least about 1 second, inone embodiment at least 1.5 seconds, and in other embodiments at leastabout 1.75 seconds. In one embodiment, the injector 10 injects themedicament at about 0.5 mL/sec., completing the injection of 1 mL inabout 2 seconds.

U.S. Pat. No. 6,391,003 discloses several experimental results ofpressures that can be applied to medicament in a glass cartridge, using26 and 27 gauge needles. The following table illustrates injections withdifferent peak pressures that can be used with glass prefilled syringes:

Pressure and Time (sec.) to Inject 1 cc Pressure 26 Gauge needle 27Gauge needle 150 p.s.i. 2.1 4.2 200 p.s.i. 1.9 3.9 240 p.s.i. 1.7 3.3375 p.s.i. 1.4 3.1

It is foreseen that higher pressures and flow rates will be used withshorter needle penetration into the patient skin to achieve jetinjections to a particular desired depth substantially withoutmedicament leakback.

It has been found that using the jet injection of the present device,short needles can be used to inject medicament to different parts of theskin, in certain embodiments subcutaneously, substantially without anyleakback. Using a needle 24 that extends by about 2.5 mm from the needleguard 66, a 27 gauge needle 24, and a pressure in the fluid chamber 22peaking at around 300 p.s.i. and ending at around 100 p.s.i., resultingin a flow rate of about 0.5 mL/sec., 1 mL of medicament has been foundto successfully be injected without leakback in close to 100% of thetested injections. Thus, the needle-assisted jet injector 10 of thepresent invention permits jet injection of the medicament using a veryshort needle reliably regardless of the thickness of the patient's skinor the patient's age, weight or other typical factors that complicatenon-jet injecting with short needles.

FIGS. 7 and 8 show another embodiment of the present invention that usesa prefilled syringe that has a long, but smaller-diameter configurationthan the embodiment of FIG. 2. While in the embodiment of FIG. 2, thefiring spring 62 extends into the bore of the prefilled syringe 18during the firing stroke, the narrower prefilled syringe 88 of injector86 does not provide as much space to accommodate a spring. Consequently,the ram 90 of injector 86 includes a bell portion 92 defining a hollowinterior 94 that is configured to receive the proximal end of theprefilled syringe 88 and the syringe support 96 when the injector 86 isfired. Similarly, a bell-receiving space 98 is defined around theexterior of the prefilled syringe 88 and syringe support 96 to receivethe bell portion 92 during the firing. The bell portion 92 includes aspring seat 100 extending radially outwardly and configured and disposedto seat a compression spring 102. When the trigger mechanism 56 isactivated and the device 86 is fired, spring 102 acts against seat 100to drive the ram 90 against plunger 104 to jet inject the medicamentfrom the fluid chamber 106. As a result, after firing, the spring 102radially surrounds the prefilled syringe 88. The outer housing portion108 is wider than outer housing portion 14 of injector 10 to accommodatethe bell portion 92 and larger diameter spring 102.

One available long configuration syringe with a 1 mL capacity has acylindrical syringe body portion with a diameter of 8.15 mm, which wouldin certain embodiments be used in the injector of FIGS. 7 and 8, whileone available shorter configuration syringe of the same capacity has acylindrical syringe body portion with a diameter of 10.85 mm, whichwould in certain embodiments be used in the injector of FIGS. 1 and 2.While the embodiment with a bell portion 92 can be used withwider/shorter syringes, in certain embodiments, the prefilled syringeshave an outer diameter cylindrical wall of less than about 10 mm, and inother embodiments less than about 9 mm.

Injector 86 also includes a cap 110 fitted around the needle guard 66,and associated with the outer housing 108 to prevent retraction of theneedle guard 66 and the triggering of the device 86. Additionally, thecap 110 seals off the needle tip 26 and can be removed prior to usingthe device 86. In one embodiment, the cap 110 is configured to fit overthe needle guard 66 in a snap-fit association therewith, such as byincluding a narrower diameter portion 112 associated with an enlargeddiameter portion 114 of the needle guard 66.

Additionally, injector 86 employs a syringe cushion cap 116 that extendsaround the outside of the syringe flange 34 from the syringe cushion 118to help trap and retain the prefilled syringe 88. In one embodiment, acushion cap 122 is connected to the cushion 118 and is, in certainembodiments, of unitary construction therewith. The cushion cap 122abuts the distal end of the syringe body 120 to radially position andhold the proximal end of the body 120 while the needle 24 is beinginserted into the patient. Similarly to the embodiment of FIG. 2, thesyringe holder 96 is associated with the housing in a substantiallyfixed position, such as by mounting portion 124, which traps protrusions126 of the syringe holder.

Referring to FIG. 9, injector 128 has a needle guard 130 configured toretract further into the injector housing than the injector of FIGS. 1and 2 or FIG. 5 before the trigger mechanism 52 fires the jet injection.The injector in this figure is shown in a position in which the triggermechanism 52 is being released and about to fire the injection. Thedistance 76 by which the needle extends past the guard 130 or the distalsurface of the guard 130 that contacts the skin in certain embodimentsbetween about 12.5 and 13 mm. In one embodiment, the guard is preferablyconfigured to reextend to a protecting position after the device isfired and removed from the patient, such as under the bias of spring 72,and is locked in that position by locking members 132, as known in theart to prevent reuse on the injector.

In other embodiments, the guard length, the location of the guardinjecting position with respect to the needle tip (including the guardthrow between the protecting and injecting positions), and the length ofthe needle from the syringe body can be selected to allow for shalloweror deeper needle insertions before the device is fired, providing lesseror greater distances 76, respectively. In one embodiment, the guard iskept from sliding further back than substantially at the firingposition, to better control in insertion depth into the patient.

Each and every reference herein is incorporated by reference in itsentirety. The entire disclosure of U.S. Patent Application 2011/0144594,U.S. Pat. Nos. 8,021,335 and 6,391,003 are hereby incorporated herein byreference thereto as if fully set forth herein.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, the featuresfor the various embodiments can be used in other embodiments, such asthe needle and guard cap of FIGS. 7 and 8, which can be applied to theembodiment of FIG. 1. Therefore, it will be understood that the appendedclaims are intended to cover all such modifications and embodiments thatcome within the spirit and scope of the present invention.

What is claimed is:
 1. An injection device, comprising: a prefilledsyringe comprising: a container portion defining a fluid chambercontaining a medicament; a needle configured to deliver the medicamentfrom the fluid chamber into an injection site; a plunger movable withinthe fluid chamber; a housing that houses the prefilled syringe and isconfigured to allow insertion of the needle at an injection location,the housing comprising: a retractable guard that is movable between aprotecting position in which the needle is disposed within theretractable guard and an injecting position in which a tip of the needleis exposed for insertion into the injection site; a biasing elementconfigured to bias the retractable guard toward the protecting position,and a locking element having at least one abutment arm, the abutment armhaving at least one tapered portion and an engagement portion axiallyadjacent to the at least one tapered portion, the engagement portionconfigured to resist the movement of the retractable guard when theretractable guard is moved from the protecting position toward theinjecting position; and an energy source configured to bias the plungerwith a force selected to produce an injecting pressure on the medicamentin the fluid chamber to inject the medicament from the fluid chamberthrough the needle to the injection site, wherein a breakaway force isconfigured to be applied to the retractable guard to overcome theresistance to movement of the retractable guard caused by the engagementportion of the abutment arm, wherein the breakaway force is equal to orgreater than a trigger force, wherein the trigger force causes injectionof the medicament.
 2. The injection device of claim 1, wherein thetrigger force is applied to the injection device to cause injection ofthe fluid from the fluid chamber into the injection site.
 3. Theinjection device of claim 1, wherein the breakaway force is greater thana frictional force from friction between the retractable guard and theinjection device as the retractable guard moves from the protectingposition toward the injecting position.
 4. The injection device of claim1, wherein the breakaway force is applied during an initial movement ofthe retractable guard toward the injecting position.
 5. The injectiondevice of claim 1, wherein the abutment arm is directly coupled to thehousing of the injection device.
 6. The injection device of claim 1,wherein the abutment arm is in a sleeve separate from the housing of theinjection device.
 7. The injection device of claim 1, wherein theabutment arm is part of a lock ring.
 8. The injection device of claim 1,wherein the injection device is a jet injection device.
 9. The injectiondevice of claim 1, wherein the engagement portion extends radiallyoutwardly relative to a longitudinal axis of the injection device. 10.The injection device of claim 1, further comprising: a second abutmentarm including a second abutment arm tapered portion and a secondabutment arm face.
 11. The injection device of claim 10, wherein the atleast one abutment arm includes a first abutment arm face and the firstabutment arm face is longer axially than the second abutment arm face.12. The injection device of claim 10, wherein the at least one abutmentarm includes a face adjacent to the engagement portion.
 13. Theinjection device of claim 10, wherein the second abutment arm face isadjacent to the second abutment arm tapered portion.
 14. The injectiondevice of claim 10, wherein the second abutment arm tapered portion islonger axially than the at least one tapered portion.
 15. An injectiondevice comprising: a locking element configured to engage a needleguard, the locking element having a body with at least one abutment armextending axially in a distal direction from the body, the at least oneabutment arm having a tapered portion and an engagement portion axiallyadjacent to the tapered portion, the engagement portion extendingradially outwardly relative to a longitudinal axis of the body, theengagement portion configured to resist the movement of the needle guardwhen the needle guard is moved at least partially from a protectingposition toward an injecting position, wherein the locking elementincludes a flap extending axially further in the distal direction thanthe at least one abutment arm.
 16. The injection device of claim 15,wherein the abutment arm is dimensioned to fit within a housing of theinjection device.
 17. The injection device of claim 15, wherein theabutment arm is coupled to a housing of the injection device.
 18. Theinjection device of claim 15, wherein the abutment arm is coupled to asleeve separate from a housing of the injection device.
 19. Theinjection device of claim 15, wherein the abutment arm is part of a lockring.
 20. The injection device of claim 15, wherein the injection deviceis a jet injection device.
 21. The injection device of claim 15, whereinthe flap is circumferentially adjacent to the at least one abutment arm.22. The injection device of claim 15, wherein the flap iscircumferentially spaced from the at least one abutment arm.